Process for converting paraffin to olefin and catalyst for use therein

ABSTRACT

The invention relates to a process for converting paraffin to olefin comprising the following steps: (a) providing a hydrocarbon feedstock containing at least one paraffin having 1 to 12 carbon atoms and at least one olefin having 2 to 12 carbon atoms; (b) providing a catalyst containing at least one Group VIA and/or Group VIIA transition metal on a solid support; (c) pretreating the catalyst by contacting the catalyst with at least one reducing gas and at least one oxidizing gas; and (d) contacting the by hydrocarbon feedstock and the pretreated catalyst at a temperature in the range of 200° C. to 600° C., preferably 320° C. to 450° C. and to a catalyst for use therein.

TECHNICAL FIELD

The present invention relates to a process for converting paraffin toolefin and to a catalyst for use therein.

BACKGROUND ART

Olefins have long been desired as feedstock for the petrochemicalindustries. They are useful in preparing a wide variety of petrochemicalgoods. Propylene is one of the most important olefin and its demand hasgrown substantially, largely due to its use as a precursor in theproduction of polypropylene for packaging materials and other commercialproducts.

Methods are known for the production of olefins. Currently, the majorityof light olefins such as ethylene and propylene are produced during thesteam cracking or pyrolysis of hydrocarbon feedstock such as ethane,propane, natural gas, petroleum liquids, naphtha and carbonaceousmaterials.

Steam cracking involves a very complex combination of reactions and gasrecovery systems. It is also highly energy intensive and givesrelatively low ethylene and propylene yields. It is known that propyleneyield from steam cracking may be improved using metathesis of olefinsmethod.

Olefins metathesis is a known type of reaction in which one or moreolefinic compounds are transformed into other olefins of differentmolecular weights. For example, propylene can be produced from olefinsmetathesis of feedstock comprising ethylene and butenes. However, thisprocess consumes ethylene and butenes which have many other downstreamuses and relatively high commercial value.

Another route for light olefin production is paraffin dehydrogenation.Dehydrogenation process provides better olefin yield than steam crackingbut exhibits rapid catalyst coking requiring frequent and costlyregeneration. Moreover, the significant capital cost of a propanedehydrogenation plant is normally justified only in cases of large-scalepropylene production units (e.g., typically 250,000 metric tons per yearor more).

Many approaches for improving light olefins production have beenattempted. For example, EP 1,129,056 B1 describes a process for theproduction of mono-olefins from gaseous paraffinic hydrocarbons byautothermal cracking. The process comprising feeding the paraffinichydrocarbons feedstock and a molecular oxygen-containing gas to anautothermal cracker wherein they are reacted by oxidativedehydrogenation to form a product comprising one or more mono-olefin(s).This process requires severe operating condition and hence high energyconsumption with low olefins yield.

U.S. Pat. No. 5,171,921 describes a process for the production of C2-C5olefins from higher olefinic or paraffinic or mixed olefin and paraffinfeedstock by contacting the higher hydrocarbon feed with a steamactivated catalyst containing phosphorous and H-ZSM-5. This processrequires high operating temperature up to 700° C.

U.S. Pat. No. 8,258,357 B2 describes an integrated process forproduction of olefin from C4 feedstock comprising butane which combinesa dehydrogenation unit with an olefins metathesis unit. This processrequires relatively high operating temperature and consumes high valuefeedstock materials like hydrogen and ethylene.

It has been observed that the disclosed processes for the manufacture ofolefins may have certain disadvantages during its implementation asdescribed above.

DISCLOSURE OF INVENTION

Therefore, it is an object of the present invention to overcome thedrawbacks of the prior arts, in particular by providing a process whichcan effectively convert the relatively low value paraffin to highervalue olefin at a mild condition.

The above object is achieved by a process for converting paraffin toolefin comprising the following steps: (a) providing a hydrocarbonfeedstock containing at least one paraffin having 1 to 12 carbon atomsand at least one olefin having 2 to 12 carbon atoms; (b) providing acatalyst containing at least one Group VIA and/or Group VIIA transitionmetal on a solid support; (c) pretreating the catalyst by contacting thecatalyst with at least one reducing gas and at least one oxidizing gas;and (d) contacting the hydrocarbon feedstock and the pretreated catalystat a temperature in the range of 200° C. to 600° C., preferably 320° C.to 450° C.

The term hydrocarbon feedstock in the present invention refers to thetotal, combined feed; including any recycle hydrocarbon streams, but notincluding any non-hydrocarbon diluents, which may be added along withthe feed according to some embodiments.

It is important for the present invention that the hydrocarbon feedstockis a mixture of at least one paraffin and at least one olefin having thesame or different number of carbon atoms. The mixture can be obtaineddirectly from a petrochemical process, for example a 65 mixed C3 streamor a mixed C4 stream from a naphtha cracking process or can be obtainedby mixing a paraffin-rich stream with an olefin-rich stream.

It is preferred that the at least one paraffin is methane, ethane,propane, n-butane, i-butane, n-pentane, i-pentane or mixtures thereof,more preferably propane, n-butane, i-butane or mixtures thereof.

It is also preferred that the at least one olefin is ethylene,propylene, 1-butene, cis-2-butene, trans-2-butene, n-pentene or mixturesthereof, more preferably is ethylene.

At least some amount of olefin in the feedstock is necessary to initiatethe conversion of paraffin to olefin according to the present invention.The at least one olefin can still be maintained in the feedstock as aco-feed or can also be excluded from the feedstock once the conversionis initiated.

It is preferred that the weight ratio of paraffins to olefins in thehydrocarbon feedstock is in the range of 0.1:1 to 100:1, more preferably0.5:1 to 10:1.

Catalysts useful in the present invention comprise at least one GroupVIA or Group VIIA transition metal on a solid support.

It is preferred that the at least one Group VIA or Group VIIA transitionmetal is molybdenum, tungsten, rhenium or mixtures thereof, preferablyis tungsten.

More preferred is that the catalyst comprises 1 to 15 percent by weightof the at least one Group VIA or Group VIIA transition metal, mostpreferably 5 to 10 percent by weight, based on total weight of thecatalyst.

It is also preferred that the solid support is silicon dioxide, aluminumoxide, activated carbon, magnesium oxide, titanium dioxide, lanthanumoxide, zirconium dioxide, zeolite, layered double hydroxides or anycombination thereof, preferably a combination of silicon dioxide andzeolite, more preferably a combination of silicon dioxide and 0.1 to 60percent by weight of zeolite, based on total weight of the solidsupport.

Further preferred the zeolite is selected from ZSM-5, X-zeolite,Y-zeolite, beta zeolite, MCM-22, ferrierrite, chabazite or mixturesthereof, preferably is Y-zeolite.

To even further improve efficiency of the process, the catalyst may bemixed or used together with a co-catalyst. Preferably, the catalyst ismixed or used together with isomerization catalyst. Isomerizationcatalyst can be selected from a group consisting of magnesium oxide,calcium oxide, yttrium oxide, zinc oxide, hydrotalcite and a solidsolution of aluminum oxide and magnesium oxide.

The catalyst of the present invention can be prepared by impregnation orpartial impregnation method which generally involves contacting thesolid support with an impregnation solution of a transition metalcompound. The impregnation conditions should be selected to achieve adesired level of transition metal on the catalyst. The preferredconditions include concentration of metal compound in the impregnationsolution in the range of 0.1·10⁻⁶ M to 5 M, impregnation temperature inthe range of 20° C. to 200° C. and contact time in the range of 1 minuteto 5 hours. Other known methods for catalyst preparation such asincipient wetness, ion exchange or the like can also be used.

The impregnation solution includes at least one transition metalcompound in at least one solvent. Many selections of transition metalcompound are possible for the present invention such as nitrate, sulfateor carbonate of the transition metal. For example, the transition metalcompound used in the catalyst preparation step is ammonium metatungstentetrahydrate.

The selected solvent for the present invention can be any suitablesolvent which can dissolve or disperse the selected metal compounds suchas oxygenated solvent and hydrocarbon solvent. For example, the solventcan be selected from water, methanol, ethanol and hexane.

Following impregnation (or other preparation methods as mentionedabove), the metal deposited support is preferably dried and thencalcined to remove moisture and volatile fractions of the metal compoundused in the catalyst preparation step. Drying conditions generallyinclude a temperature from 20° C. to 200° C. and a period from 2 hoursto 20 hours. Calcining conditions generally include a temperature from200° C. to 800° C. and a period of 1 hour to 48 hours. Both drying andcalcining steps are normally performed under an atmosphere ofoxygen-containing gas (e.g., air or oxygen). It should be pointed outthat the drying step can be combined with the calcining step, i.e.drying occurs during calcinations.

Prior to its use in the conversion reaction, the catalyst is pretreatedwith reducing gas and oxidizing gas. The use of such catalystpretreatment results in formation of metal hydride and metal oxide. Asuitable amount of metal hydride and metal oxide on the catalyst ispreferred to make the catalyst active in the conversion of paraffin toolefin according to the present invention. A proper amount of metalhydride and metal oxide can be achieved by selecting suitable conditionsfor catalyst pretreatment. That is, it is preferred that the pretreatedcatalyst comprises a mixture of at least one transition metal hydrideand at least one transition metal oxide.

It is preferred that pretreating the catalyst comprises contacting thecatalyst with the at least one reducing gas, preferably hydrogen, at atemperature in the range of 200° C. to 700° C., preferably 300° C. to600° C., preferably with a WHSV in the range of 0.0001 hr⁻¹ to 100 hr⁻¹,more preferably 0.001 hr⁻¹ to 10 hr⁻¹, and preferably for a period of 5minutes to 30 hours, more preferably 12 hours to 24 hours.

It is also preferred that pretreating the catalyst comprises contactingthe catalyst with the at least one oxidizing gas, preferably air, at atemperature in the range of 200° C. to 700° C., preferably 300° C. to600° C., preferably with a WHSV in the range of 0.0001 hr⁻¹ to 100 hr⁻¹,more preferably 0.001 hr⁻¹ to 10 hr⁻¹, and preferably for a period of 5minutes to 30 hours, more preferably 12 hours to 24 hours.

As is understood in the art, the WHSV is the mass flow of thehydrocarbon feedstock divided by the weight of the catalyst bed andrepresents the equivalent mass of feed processed every hour. The WHSV isrelated to the inverse of the reactor residence time.

In a preferred embodiment, the catalyst is first contacted with areducing gas and afterwards contacted with an oxidizing gas. In afurther preferred embodiment, the catalyst is first contacted with anoxidizing gas and then contacted with a reducing gas.

The reducing gas and the oxidizing gas can optionally be diluted withdiluents. The diluents should be nonreactive under the selected catalystpretreatment condition. Suitable diluents are, for example, nitrogen,argon, methane and the like, or mixtures thereof. The catalystpretreatment may occur shortly prior to use or in situ.

Following the catalyst pretreatment, the pretreated catalyst is thenexposed to flowing hydrocarbon feedstock in the reaction zone at properconditions to start the conversion of paraffin to olefin.

Contacting the hydrocarbon feedstock with the pretreated catalyst canoccur continuously or batch wise. Generally, the contacting is performedwith the hydrocarbon feedstock being passed continuously through a fixedbed of the catalyst in the reaction zone. A number of other suitablesystems for carrying out the feedstock/catalyst contacting are known inthe art, with the optimal choice depending on the particular feedstock,rate of catalyst deactivation and other factors. Such systems includemoving bed system, swing bed system and fluidized bed system.

It is preferred that contacting the hydrocarbon feedstock and thepretreated catalyst in step (d) is carried out at a temperature in therange of 320° C. to 450° C.

It is also preferred that contacting the hydrocarbon feedstock and thepretreated catalyst in step (d) is carried out at a pressure in therange of 1 bar to 60 bar, preferably 20 bar to 40 bar.

It is also further preferred that contacting the hydrocarbon feedstockand the pretreated catalyst in step (d) s carried out at a WHSV in therange of 0.01 hr⁻¹ to 200 hr⁻¹, preferably 0.05 hr⁻¹ to 100 hr⁻¹, morepreferably 0.1 hr⁻¹ to 20 hr⁻¹.

Under the conversion conditions described above, the hydrocarbonfeedstock is normally in the gas-phase in the reaction zone. However,the conversion reaction can also occur when the hydrocarbon feedstock isin liquid phase or mixture of gas and liquid phase.

It is normal to have separation unit(s) downstream of the reaction zonein order to separate and achieve the desired purity of the products fromthe conversion process.

Recycling of the unconverted hydrocarbon feedstock to the reaction zonemay often be desirable for achieving complete or at least significantlyhigher overall conversion than the equilibrium-limited per passconversion of the feedstock.

The catalyst employed in the inventive process normally losses itsactivity over time due to the buildup of poisonous substances, coke,carbon and/or polymer on the catalyst process, and hence requiresregeneration.

Therefore, it is preferred that the process according to the presentinvention further comprises a regeneration step as step (e) of theprocess.

Regeneration typically involves removing the poisonous substances, coke,carbon and/or polymer deposited on catalyst surface by oxidativeburning.

Preferably, the regeneration step (e) comprises contacting the catalystwith at least one oxidizing gas, preferably air, at a temperature in therange of 200° C. to 700° C., preferably 400° C. to 550° C.

Surprisingly, it was found that the inventive process provides animproved, more economical and efficient process for converting paraffinto olefin.

The examples below demonstrate the advantages achieved from using theprocess of the invention in paraffin to olefin conversion by showing thesurprising effects of certain steps and conditions of the process, inparticular by providing a process which can effectively convert therelatively low value paraffin to higher value olefin at a mildcondition.

The following examples are intended to be illustrative of this inventiononly. They are not to be taken in any way limiting on the scope of thisinvention. Numerous changes and modifications can be made withoutdeparting from the scope of the invention as disclosed in theaccompanying claims.

EXAMPLES

Examples 1 to 6 are illustrative of the process for converting paraffinto olefin according to this invention.

Example 1

3 grams of catalyst comprising 8 percent by weight of tungsten on asolid support comprising 5 percent by weight of HY-zeolite and 95percent by weight of silicon dioxide was mixed with 3 grams of magnesiumoxide and then packed in a tubular reactor.

After that the catalyst was pretreated by flowing air through thecatalyst bed at a temperature of 500° C. and WHSV 0.30 hr⁻¹ for 4 hours,then subsequently flow 10 percent by volume of hydrogen gas balancingwith nitrogen through the catalyst bed at a temperature of 400° C. andWHSV 0.002 hr⁻¹ for 1 hour and then raised temperature to 550° C. andhold for 2 hours before cooling down to reaction temperature at 350° C.

When bed temperature reached 350° C., feedstock containing 10 percent byweight of n-butane and 20 percent by weight of ethylene balancing withnitrogen was fed through the catalyst bed at flow rate 10-20 cc/min andpressure 20 barg.

Effluents from the reaction were directed to GC-FID (Agilent) to measuretheir chemical compositions. The measured compositions of effluents wereused to calculate paraffin conversions and olefin yields. The result ofthis experiment is shown in Table 1.

Example 2

An experiment the same as in Example 1 was performed with a feedstockcontaining 10 percent by weight of i-butane and 20 percent by weight ofethylene balancing with nitrogen. The result of this experiment is shownin Table 1.

Example 3

An experiment the same as in Example 1 was performed with a feedstockcontaining 10 percent by weight of propane and 20 percent by weight ofethylene balancing with nitrogen. The result of this experiment is shownin Table 1.

Example 4

An experiment the same as in Example 1 was performed with a feedstockcontaining 10 percent by weight of LPG (containing 25 wt % propane, 25wt % i-butane and 50 wt % n-butane) and 20 percent by weight of ethylenebalancing with nitrogen. The result of this experiment is shown in Table1.

Example 5

3 grams of catalyst comprising 8 percent by weight of tungsten on asolid support comprising 5 percent by weight of HY-zeolite and 95percent by weight of silicon dioxide was mixed with 3 grams of magnesiumoxide and then packed in a tubular reactor.

After that the catalyst was pretreated by flowing air through thecatalyst bed at a temperature of 500° C. and WHSV 0.30 hr⁻¹ for 4 hours,then subsequently flow 10 percent by volume of hydrogen gas balancingwith nitrogen through the catalyst bed at a temperature of 400° C. andWHSV 0.002 hr⁻¹ for 1 hour and then raised temperature to 550° C. andhold for 2 hours before cooling down to reaction temperature at 350° C.

When bed temperature reached 350° C., feedstock containing 4 percent byweight of n-butene and 6 percent by weight of n-butane and 20 percent byweight of ethylene balancing with nitrogen was fed through the catalystbed at flow rate 5-20 cc/min and pressure 20 barg.

Effluents from the reaction were directed to GC-FID (Agilent) to measuretheir chemical compositions. The measured compositions of effluents wereused to calculate paraffins conversion and olefins yield. The result ofthis experiment is shown in Table 1.

Example 6

This example is illustrative of the process for converting paraffin toolefin according to this invention.

An experiment the same as in Example 1 was performed without magnesiumoxide. The result of this experiment is shown in Table 1.

Comparative examples A and B illustrate the effect of catalystpretreatment conditions on the inventive process.

Comparative Example A

3 grams of catalyst comprising 8 percent by weight of tungsten on asolid support comprising 5 percent by weight of HY-zeolite and 95percent by weight of silicon dioxide was mixed with 3 grams of magnesiumoxide and then packed in a tubular reactor.

After that the catalyst was pretreated by flowing 10 percent by volumeof hydrogen gas balancing with nitrogen through the catalyst bed at atemperature of 400° C. and WHSV 0.002 hr⁻¹ for 1 hour, and then raisedtemperature to 550° C. and hold for 2 hours before cooling down toreaction temperature at 350° C.

When bed temperature reached 350° C., feedstock containing 10 percent byweight of n-butane and 20 percent by weight of ethylene balancing withnitrogen was fed through the catalyst bed at flow rate 10-20 cc/min andpressure 20 barg.

Effluents from the reaction were directed to GC-FID (Agilent) to measuretheir chemical compositions. The measured compositions of effluents wereused to calculate paraffins conversion and olefins yield. The result ofthis experiment is shown in Table 1.

Comparative Example B

3 grams of catalyst comprising 8 percent by weight of tungsten on asolid support comprising 5 percent by weight of HY-zeolite and 95percent by weight of silicon dioxide was mixed with 3 grams of magnesiumoxide and then packed in a tubular reactor.

After that the catalyst was pretreated by flowing air through thecatalyst bed at a temperature of 500° C. and WHSV 0.30 hr⁻¹ for 4, andthen raised temperature to 550° C. and hold for 2 hours before coolingdown to reaction temperature at 350° C. When bed temperature reached350° C., feedstock containing 10 percent by weight of n-butane and 20percent by weight of ethylene balancing with nitrogen was fed throughthe catalyst bed at flow rate 10-20 cc/min and pressure 20 barg.

Effluents from the reaction were directed to GC-FID (Agilent) to measuretheir chemical compositions. The measured compositions of effluents wereused to calculate paraffins conversion and olefins yield. The result ofthis experiment is shown in Table 1.

Comparative examples C, D, E and F illustrate the effect of olefinco-feeding on the inventive process.

Comparative Example C

3 grams of catalyst comprising 8 percent by weight of tungsten on asolid support comprising 5 percent by weight of HY-zeolite and 95percent by weight of silicon dioxide was mixed with 3 grams of magnesiumoxide and then packed in a tubular reactor.

After that the catalyst was pretreated by flowing air through thecatalyst bed at a temperature of 500° C. and WHSV 0.30 hr⁻¹ for 4 hours,then subsequently flow 10 percent by volume of hydrogen gas balancingwith nitrogen through the catalyst bed at a temperature of 400° C. andWHSV 0.002 hr⁻¹ for 1 hour and then raised temperature to 550° C. andhold for 2 hours before cooling down to reaction temperature at 350° C.

When bed temperature reached 350° C., feedstock containing 10-20 percentby weight of n-butane balancing with nitrogen was fed through thecatalyst bed at flow rate 5-20 cc/min and pressure 20 barg.

Effluents from the reaction were directed to GC-FID (Agilent) to measuretheir chemical compositions. The measured compositions of effluents wereused to calculate paraffins conversion and olefins yield. The result ofthis experiment is shown in Table 1.

Comparative Example D

3 grams of catalyst comprising 8 percent by weight of tungsten on asolid support comprising 5 percent by weight of HY-zeolite and 95percent by weight of silicon dioxide was mixed with 3 grams of magnesiumoxide and then packed in a tubular reactor.

After that the catalyst was pretreated by flowing air through thecatalyst bed at a temperature of 500° C. and WHSV 0.30 hr⁻¹ for 4 hours,then subsequently flow 10 percent by volume of hydrogen gas balancingwith nitrogen through the catalyst bed at a temperature of 400° C. andWHSV 0.002 hr⁻¹ for 1 290 hour and then raised temperature to 550° C.and hold for 2 hours before cooling down to reaction temperature at 350°C.

When bed temperature reached 350° C., feedstock containing 10-20 percentby weight of ethylene balancing with nitrogen was fed through thecatalyst bed at flow rate 5-20 cc/min and pressure 20 barg.

Effluents from the reaction were directed to GC-FID (Agilent) to measuretheir chemical compositions. The measured compositions of effluents wereused to calculate paraffins conversion and olefins yield. The result ofthis experiment is shown in Table 1.

Comparative Example E

3 grams of catalyst comprising 8 percent by weight of tungsten on asolid support comprising 5 percent by weight of HY-zeolite and 95percent by weight of silicon dioxide was mixed with 3 grams of magnesiumoxide and then packed in a tubular reactor.

After that the catalyst was pretreated by flowing air through thecatalyst bed at a temperature of 500° C. and WHSV 0.30 hr⁻¹ for 4 hours,then subsequently flow 10 percent by volume of hydrogen gas balancingwith nitrogen through the catalyst bed at a temperature of 400° C. andWHSV 0.002 hr⁻¹ for 1 hour and then raised temperature to 550° C. andhold for 2 hours before cooling down to reaction temperature at 350° C.

When bed temperature reached 350° C., feedstock containing 10-20 percentby weight of i-Butane balancing with nitrogen was fed through thecatalyst bed at flow rate 5-20 cc/min and pressure 20 barg.

Effluents from the reaction were directed to GC-FID (Agilent) to measuretheir chemical compositions. The measured compositions of effluents wereused to calculate paraffins conversion and olefins yield. The result ofthis experiment is shown in Table 1.

Comparative Example F

3 grams of catalyst comprising 8 percent by weight of tungsten on asolid support comprising 5 percent by weight of HY-zeolite and 95percent by weight of silicon dioxide was mixed with 3 grams of magnesiumoxide and then packed in a tubular reactor.

After that the catalyst was pretreated by flowing air through thecatalyst bed at a temperature of 500° C. and WHSV 0.30 hr⁻¹ for 4 hours,then subsequently flow 10 percent by volume of hydrogen gas balancingwith nitrogen through the catalyst bed at a temperature of 400° C. andWHSV 0.002 hr⁻¹ for 1 hour and then raised temperature to 550° C. andhold for 2 hours before cooling down to reaction temperature at 350° C.

When bed temperature reached 350° C., feedstock containing 10-20 percentby weight of propane balancing with nitrogen was fed through thecatalyst bed at flow rate 5-20 cc/min and pressure 20 barg.

Effluents from the reaction were directed to GC-FID (Agilent) to measuretheir chemical compositions. The measured compositions of effluents wereused to calculate paraffins conversion and olefins yield. The result ofthis experiment is shown in Table 1.

TABLE 1 Paraffin(s) Ethylene Propylene Conversion SelectivitySelectivity Example Feed Co-catalyst Pretreatment (wt %) (wt %) (wt %)Example 1 n-Butane MgO Air, H2 60 70 25 Ethylene Example 2 i-Butane MgOAir, H2 57 82 10 Ethylene Example 3 Propane MgO Air, H2 40 8 80 EthyleneExample 4 LPG MgO Air, H2 55 20 70 Ethylene Example 5 n-Butene MgO Air,H2 90 wt % of C4 hydrocarbon in feedstock n-Butane (n-Butene andn-Butane) was converted Ethylene to a product stream containing 64 wt %ethylene and 27 wt % propylene Example 6 n-Butane None Air, H2 66% 72%25% Ethylene Comparative n-Butane MgO H2 No paraffin conversion. 40% ofolefin Example A Ethylene was converted to 60 wt % propylene and 40 wt %n-butene Comparative n-Butane MgO Air No Reaction Example B EthyleneComparative n-Butane MgO Air, H2 No Reaction Example C ComparativeEthylene MgO Air, H2 No Reaction Example D Comparative i-Butane MgO Air,H2 No Reaction Example E Comparative Propane MgO Air, H2 No ReactionExample F

The paraffin conversions shown in Table 1 were calculated from weight ofparaffin(s) converted during reaction divided by total weight ofparaffin(s) in feedstock and then multiplies by one hundred. Theethylene and propylene selectivity shown in Table 1 were calculated fromweight of ethylene or propylene produced from the reaction divided byweight of all products produced from the reaction and then multiplies byone hundred. The features disclosed in the foregoing description and inthe claims may, both separately and in any combination thereof, bematerial for realizing the invention in diverse forms thereof.

1-14. (canceled)
 15. A process for converting paraffin to olefin comprising the following steps: (a) providing a hydrocarbon feedstock containing at least one paraffin having 1 to 12 carbon atoms and at least one olefin having 2 to 12 carbon atoms; (b) providing a catalyst containing at least one Group VIA and/or Group VIIA transition metal on a solid support; (c) pretreating the catalyst by contacting the catalyst with at least one reducing gas and at least one oxidizing gas; and (d) contacting the hydrocarbon feedstock with the pretreated catalyst at a temperature in the range of 200° C. to 600° C.,
 16. The process according to claim 15 wherein the at least one paraffin is methane, ethane, propane, n-butane, i-butane, n-pentane, i-pentane or mixtures thereof.
 17. The process according to claim 15 wherein the at least one olefin is ethylene, propylene, 1-butene, cis-2-butene, trans-2-butene, n-pentene or mixtures thereof.
 18. The process according to claim 15 wherein the weight ratio of paraffins to olefins in the hydrocarbon feedstock is in the range of 0.1:1 to 100:1.
 19. The process according to claim 15 wherein the at least one Group VIA or Group VIIA transition metal is molybdenum, tungsten, rhenium or mixtures thereof.
 20. The process according to claim 15 wherein the catalyst comprises 1 to 15 percent by weight of the at least one Group VIA or Group VIIA transition metal based on total weight of the catalyst.
 21. The process according to claim 15 wherein the solid support is silicon dioxide, aluminum oxide, activated carbon, magnesium oxide, titanium dioxide, lanthanum oxide, zirconium dioxide, zeolite, layered double hydroxides or any combination thereof.
 22. The process according to claim 15 wherein pretreating the catalyst comprises contacting the catalyst with the at least one reducing gas at a temperature in the range of 200° C. to 700° C.
 23. The process according to claim 22, wherein the reducing gas is hydrogen.
 24. The process according to claim 22 wherein the pretreating is done with a WHSV in the range of 0.0001 hr⁻¹ to 100 hr⁻¹ for a period of 5 minutes to 30 hours.
 25. The process according to claim 15 wherein pretreating the catalyst comprises contacting the catalyst with the at least one oxidizing gas at a temperature in the range of 200° C. to 700° C.
 26. The process according to claim 25 wherein the oxidizing gas is air.
 27. The process according to claim 25 wherein the pretreating is done with a WHSV in the range of 0.0001 hr⁻¹ to 100 hr⁻¹ for a period of 5 minutes to 30 hours.
 28. The process according to claim 15 wherein the pretreated catalyst comprises a mixture of at least one transition metal hydride and at least one transition metal oxide.
 29. The process according to claim 15 wherein contacting the hydrocarbon feedstock with the pretreated catalyst in step (d) is carried out at a pressure in the range of 1 bar to 60 bar.
 30. The process according to claim 15 wherein contacting the hydrocarbon feedstock and the pretreated catalyst in step (d) is carried out at a WHSV in the range of 0.01 hr⁻¹ to 200 hr⁻¹.
 31. The process according to claim 15 wherein the process further comprises a regeneration step (e).
 32. The process according to claim 15 wherein the regeneration step (e) comprises contacting the catalyst with at least one oxidizing gas at a temperature in the range of 200° C. to 700° C.
 33. A catalyst containing at least one Group VIA and/or Group VIIA transition metal on a solid support.
 34. The catalyst according to claim 33 wherein the at least one Group VIA and/or Group VIA transition metal is molybdenum, tungsten, rhenium, or mixtures thereof.
 35. The catalyst according to claim 33 wherein the catalyst comprises 1 to 15 percent by weight of the at least one Group VIA and/or Group VIIA transition metal, based on total weight of the catalyst.
 36. The catalyst according to claim 35 wherein the catalyst comprises 5 to 10 percent by weight of the at least one Group VIA and/or Group VIA transition metal, based on total weight of the catalyst.
 37. The catalyst according to claim 33 wherein the solid support is silicon dioxide, aluminum oxide, activated carbon, magnesium oxide, titanium dioxide, lanthanum oxide, zirconium dioxide, zeolite, layered double hydroxide or any combination thereof.
 38. The catalyst according to claim 32 wherein the solid support is a combination of silicon dioxide and zeolite.
 39. The catalyst according to claim 33 wherein the solid support is a combination of silicon dioxide and 0.1 to 60 percent by weight of zeolite, based on total weight of the solid support.
 40. The catalyst according to claim 37 wherein the zeolite is ZSM-5, X-zeolite, Y-zeolite, beta-zeolite, MCM-22, ferrierrite, chabazite, or mixtures thereof.
 41. The catalyst according to any of claim 33 wherein the catalyst comprises 8 percent by weight of tungsten on a solid support comprising 5 percent by weight of HY-zeolite and 95 percent by weight of silicon dioxide. 